Carburetor



Oct. 1, 1940. P. sc l-'IUTTLER 2,216,677

CARBURETOR Filed Jan. 50, 1939 2 Sheets-Sheet 1 7 a 5 Fu r l l c u ,j i /6 ai? .8 .5 ru I0 l m v Q 9 /4 a l //zy o 2 j x i f. 7 Mug: y l

Od. l, 1940. p. SCHUTTLER 2,216,677

CARBURETOR Filed Jan. 30, 1939 2 Sheets-Sheet 2 9 'f g o 25 i f 5 71, g 8 Q 7 I 23 1 2/ E" Q Patented Oct. 1, 1940 UNITED STATES PATENT CFFICE csnnnanroa H., Berlin, Germany Application January so, 193s, semi' No. 256,651 In Germany January 29, 1938 1 Claim.

(Granted under the provisions of sec. 14, act of March 2, 1927; 357 0. G. 5)

This invention relates to a carburetor for'internal combustion engines inwhich the liquid fuel is atomised not directly within the combustion air which the motor has sucked in, but is led to 5 an auxiliary mixing space in which a small amount of air is added to the fuel so that a superrich mixture is formed to which the main amount of air is admixed only in the main mixing space.

A thus designed carburetor presents, as is known,

advantages as regards the regulation of the amount of fuel requisite at the time being, the regulation being effected in this way that the amount of air flowing through the auxiliary mixing space and, thus, also the height of the pressure existing in this space is varied, in dependency of a throttle valve, by means of a regulating body by which the width of the inlet aperture or of the outlet aperture or of both these apertures of the auxiliary mixing space is suitably adjusted.

The provision of the auxiliary mixing space presents first of all, the possibility to arrange the air regulating device (throttle ap) serving for regulating the motor performance not behind the main mixing space, but, counter to the usual arrangement, in front of this space whereby, under circumstance, service. advantages can be attained. With this arrangement of the throttle flap the absolute pressure in the main mixing space increases with the increase of the width of the passage aperture which might entail a reduction of the supply of fuel at an increase of the performance of the. motor if the fuel would be sucked directly into the main mixing fspace. The insertion of the auxiliary mixing4 space renders possible .a reversal of the variation of the pressure at the fuel outlet place, in such a manner, that the absolute pressure in the auxiliary mixing space is reduced and the supply of the fuel is increased the more the throttle flap of the main mixing space is opened and the perfomance of the motor is correspondingly increased..

With such a carburetor, therefore, there is coordinated to every position of the throttle ap which position corresponds, inl general, with a certain definite number of revolutions of the motor, a certain definite adjustment of the regulating body pertaining to the auxiliary mixing space, whereby is rendered possible that with the simplest constructional form of the carburetor a mechanical connection between the throttle iiap and the regulating body can be provided. Instead thereof, the action of the throttle ap upon the regulating body takes place in an indirect manner with the aid of a member inserted between said parts and i so designed as to permit to displace as a whole the coordination of the positions of the regulating body. Such an alteration of the coordination is automatically obtained .if the regulating body is readjusted by means of a pressure gauge, for instance a barometric box, subject to the atmos- 5 pheric pressure and located behind the throttle flap. In this case the carburetor conveys an amount of fuel accommodated to the amount of air also if the number of revolutions of the motor and, thus, also the air-weight sucked in the unit m of tixne varies* by reason of a decrease of the load on the motor, the position of the throttle flap remaining unchanged. The, yielding connection of the two regulating devices presents also the possibility to do away in a certain degree with the 15 influence of variations ofthe atmospheric pressure upon the supply of the fuel, in that to every posititon of the throttle nap, for instance in the case of a reduction of the air pressure, automatically a position of the regulation device of 1 the 20 auxiliary mixing space is coordinated at which the amount of fuel sucked in is correspondingly reduced.y

In order to obtain a good accommodation to all circumstances arising in practical service it is. 25 anyhow, recommendable, as regards carburetors intended especially for iiying machines and being independent of the eventual existence of an arrangement and combination of members permitting variations ofthe motor load, to provide so an additional arrangement andv combination of parts by which the supply of the fuel can be cor-A rectly accommodated to the strongly varying height of the atmospheric pressure. The present invention relates to such an additional arrange- 35 ment and combination -.,of members constituting a device excellently suited `for the7 purpose in view. The solution of the problem, in connection with a carburetor having an auxiliary -mixing space for the production of a super-rich mixture, consists o in subjecting the pressure in the auxiliary mixing space, or the two air pressures determining the amount of fuel at the timebeing, viz. the pressure in thev auxiliary mixing space and the pressure in the float chamber, to the action of a regulable fore-atmosphere, that is to say, of a reduced atmospheric pressure in a fore-chamberl through whichair is passing. this pressure being so varied in dependency of the actually existing outer air pressure that the weight of fuel conveyed remains 50 accommodated under all circumstances to the airweight which the motor has sucked in. If the carburetor is equipped, instead of with a float chamber, with a pressure regulator, for instance a diaphragm regulator, as has become usual of late with the carburetor of flying machines, there then is on the one side the auxiliary mixing space and on the other hand the air side of this regulator connected up to the fore-chamber provided Iaccording to this invention, this chamber serving for the production of a fore-atmosphere in dependency of the variations of the atmospheric pressure.

The construction becomes particularly simple if 'for the production of the suitable pressure in the fore-chamber the now-of the amount of air is used with which the auxiliary mixing space is fed. It is then only necessary'to provide a connecting conduit between the fore-chamber and the iloatchamber, or the pressure regulator provided as a substitute for this chamber respectively. The fore-atmosphere -is then acted on preferably by varying the width of the air-entrance aperture of the said chamber, in which case the regulating body eecting said variation can be connected up to a barometric box. This regulating body is designed in known manner as a cone and generally so arranged that it throttles the entrance aperture of the fore-chamber more strongly if the atmospheric pressure decreases, in consequence whereof the box expands.

The device constituting the present invention is applicable also if the motor is equipped with a compressor which provides for the cylinder being supplied with a uniform amount of air per stroke Y also if the pressure of the atmospheric air decreases. In this case only the shape of the regulater.

.auxiliary mixing space and inthe float chamber lating body controlling the entrance of the air into the fore-chamber need be altered. There is then employed a conical regulating body which enlarges the entrance aperture in accordance with the decrease of the pressure of the atmospheric air. As now the compressor is active only to a certain denite minimum of the air pressure, in correspondence with its size, that is to say, is able to maintain the fullv charge-pressure only to a certain definite barometric height (socalled full-pressure height), variations in the supply of the fuel take place if that height is surpassed, these variations corresponding essentially to the variations taking place with ordinary motors, i. e. such operating without a compressor. It is suited to the Purpose in view to provide the carburetors intended to cooperate with motors operating with a compressor with a double regulating .body forgthe regulating-ofthe foreeatmosphere, of which body the one part enlarges the width of the entranceape'rture of said chamber in accordance with'the decrease of the `atmospheric lpressure until the so-called full-pressure height has been ,-attained. Whereas, when this height is surpassed, the other part of said double regulating body comes into action land decreases the width or the entrance-sperme or uneV fore-chamber when the atmospheric pressure decreases.

The invention is ,on the following consideration: If a lower-'atmospheric pressure acts upon av carburetor equipped with an auxiliary mixing space, three places of the carburetor are subject to that variation, viz. the pressure in the main mixing space, the pressure in the auxiliary mixing space, and the pressure in the float chamber or-in the air-space of the diaphragm regu- '111e reduction of the pressure in the or the equivalent therefor do not'compensate one another, but produce a reduction of the head effecting the outflow of the fuel, this reduction being proportionally equal to the reduction' of the barometric pressure. The reduction of the pressure in the main mixing space, eifects likewise, in cooperating with the reduction of the pressure in the outer space, a reduction of the head determining the amount of air sucked in, this reduc- 5 tion being in a certain denite ratio to the reduction of the barometric air pressure. Thus, in so far, if all dimensions are. suitably chosen, an automatic compensation of all variations could be attained without any particular contrivance. With a decrease of the atmospheric pressure the heads in the carburetor which determine the supply of the air and thefuel become smaller so that the proportion of the spatial quantities of air and fuel conveyed per second remains unchanged. But the proportion of the weights of said two substancesl conveyed per second does not remain unchanged, as the density of the air (its specific weight) is reduced in correspondence with the reduction of the outer air, whereas the density of the fuel (its specinc weight) is not reduced. The air-fuel-mixture supplied into the auxiliary mixing space becomes then poorer in air or, in other words, the motor received a comparatively too large amount of fuel. This can be obviated by reducingr the'head determining the supply of the-fuel more strongly than head determining the supply of the air. i

Now, this is attained, according to' this inven tion, iirst of all, by the provision of a foreatmosphere in which the pressure is varied not in correspondence with-the pressure of the atmospheric pressure but in a higher degree, as suited to the object in view, this increase of the pressure being proportionally equal .to the increaseot the barometric variation .at theA time being. From -this fore-atmosphere the pressures are drawn which determine the supply of the fuel. If, however, the motor with a com-v pressor which renders the weight of the air with which the motor is fed independent of the variations of the pressure of the atmospheric air up to a certain denite barometric height, there then is obtained, as it were, a reversal of said conditions as long as that height is not surpassed. It has already been mentioned that the pressure-difference determiningthe 4.outiiow of' the fuel varies in simple dependency of the outer pressure, `whereas now the air-weight conveyed to the motor remains unchanged if the charging pressurerinfrontf the inlet valvewremainsfunchanged. The supply of fuel to the auxiliary mixing space is, therefore, in this case too small,v but this can be corrected by compensating the variation of the atmospheric pressure by means of an oppositely acting fore-atmosphere. The carburetor intended for cooperation with a compresser thus, with a certain strongest reliefofthe atmoaphereiftissituated inthe proximity of the ground, and the'reiiet decreases Y, inthesamemeasureinwhich theyingmachine rises. The decrease of the relief.- or of the throttling at the entrance to the fore-chamber lasts, however, only until the above-mentioned fullpressure height has been reached. If'the machine rises still higher, the throttling'. must again be increased progressively as now the air-weight with which the motor is supplied per stroke decreases gradually, this taking place in a higherv degree than with the weight 'of the fuel, as has 'n already been mentioned.

The invention is illustrated diagrammatlcally .and .by way of example in the accompanying drawings in which are shown four oonstructional formaatthieinvention.thegurssliowing,how'- ever, only the members indispensably requisite utilized for the compression oi' the air equal to understand the invention, whereas all other members have been omitted for the sake of clearness.

In the drawings,

Fig. 1 is a vertical sectional view through a' carburetor lembodying the invention,

Fig. 2 is a similar view illustrating a modied form of the invention,

Fig. 3 is a similar view illustrating another modified form of the invention, and

Fig. 4 is a similar view illustrating another modification of the invention.

' In the exampleillustrated in Fig. 1* is supposed mixing space 4 which has an air inlet aperturel 5 and a mixture outlet aperture 6. The sectional areas of said two apertures are controlled by means of either accurately or approximately conically shaped regulating bodies 1 and 8 secured to a rod 9 coupled with the throttle flap by means of a forked lever I and a pin in connecting the forked end of vthis lever with said rod. The fuel enters into the auxiliary mixing space 4 through the delivery nozzle II which receives the fuel from the float chamber I2.

Now, there is provided, according to this invenl tion, a forechamber I3 in which is produced a fore-atmosphere in a certain denite dependency of the atmospheric pressure eldsting at the time being. It is suited to the object in view to arrange said fore-chamber I3 in such a manner that the auxiliary mixing space 4 can draw the small amount of air which it requires directly from said fore-chamber. The controlled inlet of the auxiliary mixing space forms, thus, at the same time the outlet of the fore-chamber which is connected with the air space of the float chamber I2 through the conduit I4. 'Ihe air sucked from the fore-chamber I3 into the auxiliary mixing space flows into said chamber I3 through an aperture I likewise subjected to the action of a regulating body I6. At the highest barometric air pressure to be reckoned with this regulating body I6 assumes a certain definite position by which a certain fall of pressure in the forechamber relatively to the pressure of the atmospheric air is produced. If this latter pressure falls, the regulating body I6 will be so shifted that the sectional area of the inlet aperture I5 is reduced and, thus, the fall of pressure in the fore-chamber I3, that is to say, the absolute pressure of the fore-atmosphere, is varied in a correspondingly higher degree. 'Ihe readjustment of the regulating body can be effected automatically by means'of a barometric box I1 which contains in known manner a certain definite quantity of gas and the outer surface is accessible to theV action of the atmospheric air. If the carburetor is intended for `flying machines it is suited to the purpose -in view to mount the box in a closed space I8. which is connected by a pipe I9 with a damming-up space located at a side of the air-inlet aperture I of the carburetor, so that in the case of the wind due to the flight being conditions exist at all air supply places.

' In the next example illustrated in Fig. 2 the carburetor per se is designed in the same manner as in Fig. 1, but for the float chamber I2 a diaphragm regulator 2| -is substituted. The chamber 22 of this regulator isiilled with fuel and communicates with the nozzle II that extends into the auxiliary mixing space through a conduit, as shown. The-supply of the fuel into the chamber 22 is regulated by means of the valve 23 which is actuated by the diaphragm of the regulator 2l. The oppositely located` chamber 24 is acted on by the variable air-pressure, that is to say, it is acted on, according to the present invention, by the pressure of the fore-atmosphere in the fore-chamber I3, with which the chamber 24, is connected by the pipe I4.

The further examples illustrated in the Figs. 3

and 4 correspond in general with those shown 20 in the Figs. 1 and 2, but there is in these cases the regulating device 1, 8 of the auxiliary mixing space coupled with the throttle flap not directly, but the readjustment is effected by means of a barometric box 25 enclosed in a chamber 2E connected up to the main mixing space 3. Instead of the box 25 it is, of course, possible to make use of a spring-actuated piston located in a cylinder. y

If, on opening the throttle valve, the pressure in the main mixing space rises, this increased pres- `sure acts upon the box 26 whereby the regulating device 1, 8 will be readjusted in a manner similar to said device being directly coupled with the throttle flap 2. But an additional feature of this constructional form is that the range of the readjustability of the regulating device 1, 8 differs from that of the throttle flap, in that to every position of the throttle flap another position of the regulating device in dependency of the numberv of revolutions of the motor, or of the pressure existing in the main mixing space and depending on the number of revolutions respectively, can be coordinated. 'Ihe modiiication of the carburetor operating with an auxiliary mixing spaced does not pertain to the present invention, but has been-added merely for the sake of completeness, especially for the purpose of elucidating the constructive details if a compressor is inserted between the carburetor and the motor.

Concerning the manner of operation of the device constituting the present invention it will, for the first, be sufiicient to consider the example illustrated in Fig. 1. If the flying machine flies in a uniform height the outer air-pressure can be assumed as being unvariable. In the inlet branch I and in the damming-up space 2II exists always the same air-pressure, independent of the number .of revolutions, o r the performance, of the motor, in the main mixing space, however, the absolute pressure rises uniformly, when the performance of the motor increases, from its smallest value to its greatest value at full load, but also this value remains always below the airpressure at the inlet I, or in the damming-up space 20 respectively, on accountoi' the considerable speed of the a-ir streaming to the motor. In the auxiliary mixing space 4 exists a pressure Which is always higher than the pressure in the main mixing space 3. While the pressure existing in this space riseswith an` increase of the performance of the motor, it falls at the same time, and, in fact, stronger, in the auxiliary mixing space, in that the inlet aperture 5 is reduced and the outlet aperture 6 is enlarged when the throttle nap is opened. This fall of pressure in chamber I2 rises, the supply of the fuel does not` depend solely on the change of the state in the auxiliary mixing space l, but on the difference between the pressure in the spaces I2 and 4 this difference increasing with the increase of the pressure in the forechamber, so that the desired increase of the fuel supply Vis obtained. The determination of the quantity of fuel to be supplied to the respective motor is attained by a suitable conguration of the regulating bodies 1 and 8.

If, however, at any given performance, that is to say, at a given position of the throttle ap, as well as of the regulating bodies 1 and 8,*the outer air pressure changes, for instance by reason of a change of the position of height of the flying machine, then the position of the` three regulating bodies 2, 1 and l remains unchanged, whereas the regulating body il. gets gradually readjusted in correspondence with the change of the outer air pressure, for instance in such a manner that it exerts a stronger throttling action when the outer air-pressure deccases.

It has aleady been mentioned that-the pressure in the main'mixing space decreases inthe same proportion as the pressure in the inlet branch I, the damming-up space 2U, and in the box'space I8, in consequence whereof also the fall of pressure from rwhich the supply of the air in relation to the space concerned depends is reduced in the same measure. But the reduction of the air supply, related to the weight of the air, is stronger, in that at the same time also the density of the air streaming into the motor decreases. Itis, therefore, not sufficient to reduce the fuel supply in proportion to the reduction of the outer air pressure, but the fuel supply must be reduced in a higher measure. by the readjustment of the regulating body I6 in the fore-chamber Il in such a manner that a stronger fall of pressure takes place by which l air so that it is subject also fall in the float chamber I2, as well as in the auxiliary mixing space I, a correspondingly stronger reduction of the vpressure and, thus, also a stronger reduction of the active head is caused.

It is, by the way, possible to design the box IIl in such a manner that it exerts a controlling action not only in dependency of variations of the air pressure, but' also, quite generally, in. correspondence with changes of the weight of the to influences due to the temperature. i

If the carburetor is to be used in connection with a compressor inserted between -the same and the motor, it is advisable to employ instead r-of the single regulating body I6 a double regulati-.ing body V21, 2l as shown in Figs. 3 and 4 of the This is effected If the flying machine is on the ground and the' air pressure is the highest possible the part 21 of the regulating body is in its extremethrottling position and the forechamber is, if the motor is running, under a. correspondingly strongly reduced pressure. kThe fuel supply is so determined that it corresponds to the full perfomance at the corresponding position of all movable members. An intended variation of the motor performance is attained by simultaneous readjustment of the pressure to be maintained by the regulating device for the pressure which the charge is to have, and of the regulating device 1, 8 of the auxiliary mixing space. If the flying machine gets, however, into a greater height without the performance of the motor having been readjusted there would fall, on the one in that the sectional'v area ofthe aperture I5 is A enlarged in proportion to the reduced outer 'airpressure, whereby the pressure in the fore-chamber is increased so that this pressure can uphold its original value and, therefore, the pressure existing in the spaces 22 and I and playing a part in the supply of the fuel remain unaffected. ,The dimensions of the regulating lbodies 21, 28 are such that the second part becomes active when the flying machine has risen to full-pressure height. Above this height a motor provided with a compressor is subject to the'same conditions asa motor having no compressor, in that at a greater position of height of the flying machine the weight of the air flowing into the motor commences to become lower, in fact in ahigher' degree than corresponds to the decrease of the outer air pressure. The regulating body 28 now entering into the aperture lI5 causes a deeper fall of the pressure existing in the fore-chamber I3 whereby the compensation of the fuel supply is obtained in the same manner as has already been described with respect to Fig. 1.

I claim.: In a carburetor for internal combustion engines havingamainmixing chamber and an auxiliary mixing chamber communicating with said main mixing chamber, a fuel chamber,

. means for regulating the supply of fuel to said fuel chamber.. a fuel supply conduitv leading from said fuel chamber to said auxiliary mixing chamber, an air supply chamber communicating with said auxiliary mixing chamber, means for regulating the cross sectional area of the passages leading from said air supply chamber to said auxiliary mixing chamber and from the latter to said main mixing chamber, an air supply conduit leading to said air supply chamber, lmeans responsive to the pressure in said air supply conduit in advance of said air supply chamber for regulating the cross sectional area of the passage from said air supply conduit to said air supply dchamber, and means for connecting the air supply chamber with said fuel supply regulating meairwhereby the action of said fuel regulating means is modulated by variations in pressure in said air supply chamber.

PAUL scn''rrma. u 

